I have
written an short article on a caching pattern that I use on
dotnetkicks.com and which I call the 'Reluctant Cache' pattern (does anyone know if there is a formal name for this pattern?).
It allows items to be placed in the cache only once they have reached a
threshold level of requests within a configurable time period. The
result is that only the most frequently accessed data will be cached
resulting in memory savings for your server.
1: public static List<Customer> GetCustomers() {
2: string cacheKey = "Customers";
3: int cacheDurationInSeconds = 5; //an artificially low number for demonstration
4:
5: object customers = HttpRuntime.Cache[cacheKey] as List<Customer>;
6:
7: if (customers == null) {
8: customers = CustomerDao.GetCustomers();
9:
10: if (new ReluctantCacheHelper(cacheKey, cacheDurationInSeconds, 2).ThresholdHasBeenReached) {
11: HttpRuntime.Cache.Insert(cacheKey, customers, null, DateTime.Now.AddSeconds(cacheDurationInSeconds), System.Web.Caching.Cache.NoSlidingExpiration);
12: }
13: }
14:
15: return (List<Customer>)customers;
16: }
As you can see, it only adds one extra line to our cache helper class. The
ReluctantCacheHelper class keeps a count of any requests for a particular item over a period of time. If this request count reaches a configurable threshold, it inserts the item into the cache.
A simple demonstration of this illustrates the point. If the list of customers are requested more than once in a five second period, they are placed in the cache.
Source code is also available.
on
dotnetkicks.com